The present invention relates generally to the delivery of drugs to patients, particularly to systems for providing drug delivery, and specifically, to systems for providing continuous drug delivery.
Certain drugs rarely achieve their maximum therapeutic action through conventional injection techniques. The therapeutic activity of such a drug is improved considerably when it is delivered at controlled rates to maintain optimum drug concentration for a specific period. In a typical drug injection, a greater dosage than necessary must be administered to keep the drug concentration within the effective therapeutic margin for the minimum period needed for treatment. With controlled drug infusion, the drug can be given at a precise rate that will keep the drug serum concentration within the therapeutic margin and out of the toxic range. Continuous drug delivery is assuming an ever increasing role in the treatment of acute and chronic illnesses. Many drugs reach their full potential only through precise delivery over an extended period of time.
Continuous intravenous infusion has been the only conventional method of administering drugs at constant controllable rates for prolonged periods. Conventional equipment requires the patient to be hospitalized and attended by medical professionals frequently. These requirements make the system somewhat impractical and expensive for a non-critical patient who could be treated outside the hospital.
One system for providing continuous drug delivery to a patient at a controllable rate which does not require frequent medical attention and which allows the patient to be ambulatory is a syringe pump. However, a need has arisen in drug delivery systems and especially in syringe pumps for mechanisms for interrupting the normal advancement of the plunger assembly in the reservoir and sounding an audible alarm under certain actuation conditions, such as occluded catheter and empty reservoir. It is further necessary to limit the pressure generated by the drug delivery system in the event of an occlusion. It is advantageous to interrupt the normal operation of the system and sound an alarm as promptly as possible following an occlusion or empty reservoir condition. It is also advantageous to be able to adjust the threshold of pressure necessary to actuate the interruption of operation and alarm.